Merge pull request #1 from mgoodfellow/hash-previous-backup-output

Write a hash file and handle updates etc.

README.rst

@@ -17,6 +17,7 @@ It supports the following features:
 -  Plan based backups
 -  Custom command run pre-backup
 -  Storing to S3
+-  Calculating MD5 hashes of the backup set to avoid uploading duplicate backup sets
 -  Emailing the result of the backup plans
 -  Python standard logging framework
 
@@ -54,6 +55,7 @@ file
       "AWS_REGION": "this is a region",
       "EMAIL_FROM": "source@address.com",
       "EMAIL_TO": "recipient@address.com",
+      "HASH_CHECK_FILE": "plan_hashes.txt",
       "Plans": [
         {
           "Name": "MySQL Backup",
@@ -108,11 +110,34 @@ Run the backup tool using the following method:
 
     s3backup.run_plans()
 
-See ``test.py`` in the ``src`` folder for an example.
+See ``test.py`` for an example.
+
+File Hashing
+------------
+
+After a backup set is created an MD5 hash is calculated for it. This is then compared against a previously calculated
+hash for that particular plan name.
+
+**NOTE:** Do not change the generated HASH_CHECK_FILE!
+
+Finally, be aware of a "gotcha" - the hashes are keyed on the *plan name* - therefore changing the plan name will
+cause the backup script to think it needs to upload a new backup set.
+
+Emails
+------
+
+An email will be sent after each plan runs. The email will either report a success or a failure. In the event
+of a success, it will be reported if there was a new uploaded backup set (and the file name), otherwise it will
+state that no changes were detected and no upload was made.
+
+If there was a failure while running the backup, the exception message will be emailed, and the logs can be
+referred to for further information.
 
 Future Improvements
 -------------------
 
 These are some of the planned future improvements:
 
 -  Run multiple pre-backup commands (by providing an array)
+-  Allow custom format strings for the output files (instead of the default date/time format)
+-  Modification of the glob2 library to allow hidden files to be included

S3Backup/__init__.py

@@ -31,7 +31,7 @@
 
 class S3BackupTool:
 
-    def __init__(self, config_file="config.json", log_file="s3backup.log"):
+    def __init__(self, config_file="config.json"):
         logger.info('Initialising...')
 
         try:
@@ -52,17 +52,42 @@ def run_plans(self):
             logger.info('Executing plan %d of %d', counter, len(self.PLANS))
 
             try:
-                plan.run()
-                self.__send_status_email(plan, True)
+                updated, output_file = plan.run()
+                self.__send_success_email(plan, updated, output_file)
             except Exception, e:
                 logger.error('Failed to run plan: %s', e)
-                self.__send_status_email(plan, False, e)
+                self.__send_failure_email(plan, e)
 
             counter += 1
 
         logger.info('Finished running backup plans')
 
-    def __send_status_email(self, plan, success, exception=None):
+    def __send_success_email(self, plan, updated, output_file):
+        subject = '[S3-Backup] [SUCCESS] - Plan: %s' % plan.name
+
+        body = 'The backup plan, %s, run at %s was SUCCESSFUL\n\n' % (
+            plan.name,
+            strftime("%a, %d %b %Y %H:%M:%S +0000", gmtime()))
+
+        if updated:
+            body += 'The backup set had changed, so a new backup was uploaded: %s' % output_file
+        else:
+            body += 'The backup set had not changed. No new backup uploaded'
+
+        self.__send_status_email(subject, body)
+
+    def __send_failure_email(self, plan, exception):
+        subject = '[S3-Backup] [FAILURE] - Plan: %s' % plan.name
+
+        body = 'The backup plan, %s, run at %s was a FAILURE\n\n' % (
+            plan.name,
+            strftime("%a, %d %b %Y %H:%M:%S +0000", gmtime()))
+
+        body += '\n\nDetailed failure information:\n\n%s' % exception
+
+        self.__send_status_email(subject, body)
+
+    def __send_status_email(self, subject, body):
         if self.CONFIGURATION['EMAIL_FROM'] is None or self.CONFIGURATION['EMAIL_TO'] is None:
             logger.debug('Email not provided, so status update not sent')
             return
@@ -72,25 +97,13 @@ def __send_status_email(self, plan, success, exception=None):
             aws_access_key_id=self.CONFIGURATION['AWS_KEY'],
             aws_secret_access_key=self.CONFIGURATION['AWS_SECRET'])
 
-        result = 'SUCCESS'
-        if not success:
-            result = 'FAILURE'
-
-        body = 'The backup plan, %s, run at %s was %s' % (
-            plan.name,
-            strftime("%a, %d %b %Y %H:%M:%S +0000", gmtime()),
-            result)
-
-        if exception is not None:
-            body += '\n\nDetailed failure information:\n\n%s' % exception
-
         try:
             conn.send_email(
                 self.CONFIGURATION['EMAIL_FROM'],
-                '[S3-Backup] [%s] - Plan: %s' % (result, plan.name),
+                subject,
                 body,
                 [self.CONFIGURATION['EMAIL_TO']])
         except Exception, e:
-            logger.error('Failed to send email to {0:s} regarding plan: {1:s}'.format(self.CONFIGURATION['EMAIL_TO'],
-                                                                                      plan.name),
+            logger.error('Failed to send email to {0:s} with subject {1:s}'.format(self.CONFIGURATION['EMAIL_TO'],
+                                                                                   subject),
                          e)

S3Backup/config_loader.py

@@ -28,7 +28,7 @@
 
 logger = logging.getLogger(name='config_loader')
 
-required_root_values = ['AWS_KEY', 'AWS_SECRET', 'AWS_BUCKET', 'AWS_REGION', 'Plans']
+required_root_values = ['AWS_KEY', 'AWS_SECRET', 'AWS_BUCKET', 'AWS_REGION', 'HASH_CHECK_FILE', 'Plans']
 optional_root_values = ['EMAIL_FROM', 'EMAIL_TO']
 
 def config_setup(config_file):
@@ -39,6 +39,7 @@ def config_setup(config_file):
         'AWS_SECRET': '',
         'AWS_BUCKET': '',
         'AWS_REGION': '',
+        'HASH_CHECK_FILE': '',
         'EMAIL_FROM': None,
         'EMAIL_TO': None
     }

S3Backup/hash_file.py

@@ -0,0 +1,64 @@
+import hashlib
+import os
+from shutil import move
+from tempfile import mkstemp
+
+BLOCKSIZE=65535
+
+def find_hash(hash_file, plan_name):
+    # Try to find the hash in the hash file
+    filename = os.path.normpath(hash_file)
+    if os.path.isfile(filename):
+        plan_hashes = open(filename, 'r').readlines()
+        for line in plan_hashes:
+            parts = line.strip().split('=')
+            if len(parts) == 2 and parts[0] == plan_name:
+                return parts[1]
+
+    return None
+
+def update_hash(hash_file, plan_name, hash_value):
+    # Do the update (create the file if it doesn't exist)
+    filename = os.path.normpath(hash_file)
+
+    # If it doesn't exist, we shortcut this
+    if not os.path.isfile(hash_file):
+        with open(hash_file, 'w') as new_file:
+            new_file.write('%s=%s\n' % (plan_name, hash_value))
+        return
+
+    # Otherwise, we need to rebuild the file
+    fh, abs_path = mkstemp()
+    is_written = False
+
+    with open(abs_path, 'w') as new_file:
+        with open(filename, 'r') as old_file:
+            # Handle existing entries in the file
+            for line in old_file:
+                parts = line.strip().split('=')
+                if parts[0] == plan_name:
+                    is_written = True
+                    new_file.write('%s=%s\n' % (plan_name, hash_value))
+                else:
+                    new_file.write(line)
+
+            # If the hash wasn't already in the file
+            if not is_written:
+                new_file.write('%s=%s\n' % (plan_name, hash_value))
+
+    os.close(fh)
+
+    # Remove original file
+    os.remove(hash_file)
+
+    # Move new file
+    move(abs_path, hash_file)
+
+def calc_hash(filename):
+    hasher = hashlib.md5()
+    with open(filename, 'rb') as afile:
+        buf = afile.read(BLOCKSIZE)
+        while len(buf) > 0:
+            hasher.update(buf)
+            buf = afile.read(BLOCKSIZE)
+    return hasher.hexdigest()

S3Backup/plan.py

@@ -29,6 +29,7 @@
 from zipfile import ZipFile
 import time
 import boto.ses
+from S3Backup import hash_file
 
 required_plan_values = ['Name', 'Src', 'OutputPrefix']
 optional_plan_values = ['Command']
@@ -52,6 +53,8 @@ def __init__(self, raw_plan, configuration):
         self.command = None
         self.output_file = '%s_%s.zip' % (raw_plan['OutputPrefix'], time.strftime("%Y-%m-%d_%H-%M-%S"))
 
+        self.new_hash = None
+
         if 'Command' in raw_plan:
             self.command = raw_plan['Command']
 
@@ -63,7 +66,9 @@ def run(self):
             The plan is run in the following order:
                 1) (if applicable) Run the external command provided
                 2) Zip source file(s) to destination file
-                3) Upload destination file to S3 bucket
+                3) Perform hash check to see if there are any changes (which would require an upload)
+                4) Upload destination file to S3 bucket
+                5) Update hash file with new hash
         """
         logger.info('Running plan "%s"', self.name)
 
@@ -74,12 +79,24 @@ def run(self):
         # 2) Zip the source file to the destination file
         self.__zip_files()
 
-        # 3) Upload destination file to S3 bucket
+        updated = False
+
         try:
-            self.__upload()
+            # 3) Perform hash check to see if there are any changes (which would require an upload)
+            if not self.__hash_check():
+                # 4) Upload destination file to S3 bucket
+                self.__upload()
+
+                # 5) Update hash file with new hash
+                self.__update_hash()
+
+                updated = True
+
         finally:
             self.__cleanup()
 
+        return updated, self.output_file
+
     def __run_command(self):
         logger.info('Executing custom command...')
 
@@ -137,6 +154,27 @@ def __upload(self):
             logger.error('Failed to upload backup file to S3: %s', e)
             raise
 
+    def __hash_check(self):
+        previous_hash = hash_file.find_hash(self.CONFIGURATION['HASH_CHECK_FILE'], self.name)
+
+        if previous_hash is None:
+            logger.debug('No previous hash found for plan %s', self.name)
+        else:
+            logger.debug('Got a previous hash for plan %s of %s', self.name, previous_hash)
+
+        self.new_hash = hash_file.calc_hash(self.output_file)
+
+        logger.debug('New hash for plan %s of %s', self.name, self.new_hash)
+
+        return previous_hash == self.new_hash
+
+    def __update_hash(self):
+        if self.new_hash is None:
+            logger.error('Could not update hash as no hash was found')
+            return
+
+        hash_file.update_hash(self.CONFIGURATION['HASH_CHECK_FILE'], self.name, self.new_hash)
+
     def __cleanup(self):
         logger.info('Cleaning up temporary file: %s', self.output_file)
         try:

TODO.md

@@ -1,4 +1,5 @@
 # Features to be added
 
 1. Ability to choose custom format strings on output file (rather than automatically appending date/time)
-2. Ability to run multiple commands
+2. Ability to run multiple commands
+3. Modify the glob2 library to support hidden files

config.json

@@ -5,6 +5,7 @@
   "AWS_REGION": "this is a region",
   "EMAIL_FROM": "source@address.com",
   "EMAIL_TO": "recipient@address.com",
+  "HASH_CHECK_FILE": "plan_hashes.txt",
   "Plans": [
     {
       "Name": "MySQL Backup",